Lamps and sockets with a twist-lock mechanism are conventionally known. For example, U.S. Pat. No. 6,290,522 to Campolo, the entire contents of which are incorporated herein by reference, show a conventional twist-lock socket. U.S. Pat. No. 5,816,837 to Henrici and U.S. Pat. No. 7,097,327 to Barton, the entire contents of each of which are hereby incorporated by reference, also show examples of conventional twist-lock sockets. In a conventional twist-lock socket as shown in the above reference, contact pins provided on an end cap of a lamp are slid into a groove in the socket. Once inserted into the socket, the lamp is rotated about its long axis, which brings the pins of the lamp into contact with electrical terminals provided within the socket.
In the field of lamps and lamp bulbs, it will be appreciated that certain lamps may be used with or rated for certain magnitude power supplies. Accordingly, if a lamp is coupled with a socket connected to an inappropriate power supply, it is possible that damage can be caused to the lamp and/or socket, and there could be a risk of fire and sparking that could cause damage to property or injury to persons. In conventional devices there is no mechanism to prevent improper coupling between mismatched lamps and sockets. Thus, conventional sockets and lamp end caps can pose safety risks to users and property.
Therefore, it is desirable to develop a twist-lock socket structured to prevent or “lock out” certain end caps from coupling with the socket, thus helping to ensure that an appropriate lamp bulb can be coupled with a particular socket.